The present invention relates to a means for heating fluid with solar radiation, and more particularly to a solar panel to collect thermal energy from the sun.
Due to the present energy situation, in which the cost of fossil fuel is increasing substantially and inventories of fuel are dwindling, there has been increasing emphasis on extracting thermal energy from alternative energy sources. One such alernative source is solar radiation.
Solar radiation has advantages as a source of thermal energy with respect to conventional fossil fuels. For example, the supply of solar radiation is practically unlimited; whereas fossil fuel sources are diminishing and eventually will be exhausted. Also, solar radiation can be tapped by individual homeowners without dependence upon large, centralized distribution sources such as electrical generating facilities, virtually outside the control of the homeowner. Frequent blackouts and rate increases illustrate problems of such centralized distribution which can be avoided by the homeowner utilizing solar power. However, for the individual homeowner to be able to take advantage of a solar energy system, the capital cost of the system must be low; operation must be cost-efficient; and it must be easy to install.
Solar energy collector panels are now available designed to convert solar energy into thermal energy. Most panels of this type include an absorber plate made of metal or some other high thermally conductive material which receives the solar radiation. The absorber plate intercepts solar radiation and converts a portion of it into thermal energy. The solar panels described in U.S. Pat. Nos. 3,995,615; 4,038,967; 4,048,981; 4,049,046 are examples of panels which rely on use of such an intermediate metallic or other conductive plate. A heat transfer fluid, e.g., a liquid such as water, is passed along the absorber plate in direct thermal contact therewith, such as in channels which are formed in or on the plate, to convey the thermal energy from the plate for use to heat, for example, a swimming pool or living space.
Other solar panels have been designed which, rather than relying on an intermediate absorber plate, include a shaped, metallic sheet providing a reflective surface to intercept the solar radiation and reflect it to a fluid to be heated. The collector described in French Pat. No. 76 34055 (publication no. 2 334 069) is an example of such a collector. Collectors of this type are not widely used in view of the relatively inefficient method by which the solar radiation is converted to thermal energy.
It will be seen from the above that most solar collection panels include a metal sheet, either to utilize the solar-absorptive and thermal-conductive properties of the metal, or the reflective properties thereof. Metal, however, is relatively heavy and often expensive. Most solar panels also include a metal frame to provide structural rigidity.